1. Field of the Invention
This invention relates to a roller assembly for spreading a processing liquid across an exposed film unit and, more particularly, to means for removing particulate matter from at least one of the rollers of the assembly.
2. Description of the Prior Art
In photographic apparatus of the self-developing type, a processing liquid is spread across an exposed photosensitive area of a sheet of photographic film so as to initiate the formation of a visible image. In some applications the processing liquid is applied to the surface of a roller which, in turn, applies the processing liquid to the exposed sheet of film. This liquid, if allowed to evaporate, leaves a deleterious residue on the roller which adversely affects future coating operations. Accordingly, means have been provided for removing the processing liquid after the coating operation. E.g., see U.S. Pat. Nos. 3,357,337 and 3,271,187 wherein wiper blades are used to remove such residue from the peripheral surface of a roller.
In other applications, the apparatus for spreading the processing liquid across the exposed photographic film comprises a pair of juxtaposed rollers between which the film is adapted to be advanced, either manually or by having one of the rollers driven by a motor. In one such application (see U.S. Pat. No. 3,590,707) the processing liquid is spread between an exposed photosensitive sheet and a superposed image-receiving sheet so as to initiate the formation of a visible image in the latter. During the spreading operation, some of the processing liquid may accidentally leak from between the lateral edges of the superposed sheets and be deposited upon the surface of one of the rollers. As is well known in the art, if this liquid is allowed to dry upon the roller, it will leave a residue thereupon which, like other particulate material, may adversely affect the future spreading of processing liquid between the superposed sheets of subsequent film units. It is for this reason that the spread roller assembly of U.S. Pat. No. 3,590,707 is automatically elevated to an inspection and cleaning position upon opening the back of the camera.
The accidental leakage of processing liquid from between the edges of the superposed sheets of the film unit during the spreading operation has been greatly reduced since the introduction of integral type film units of the type disclosed in U.S. Pat. No.4,005,446 and in German Pat. No. 2,522,603. This is accomplished, at least in part, by sealing the superposed edges with a mask. However, the problem of keeping the surfaces of the rollers free from foreign matter, such as that caused by accidental edge leakage, transfer of particles of sheet material from the film unit itself to the roller, etc., still remains a reality, as evidenced by the aforementioned German patent. In this patent, the opening to the film chamber is sized such that the user thereof may reach the rollers with cleaning means so as to enable cleaning thereof. But, this solution requires frequent inspections by the user in order to be effective. Accordingly, it can be seen that there is a need for a simple, inexpensive means for automatically removing foreign material from the surface of a roller.